Apple offers four standard configuration models. The new entry-level $1199 21.5-inch iMac has a 2.5GHz Core i5 quad core processor, a 500GB hard drive, and AMD Radeon HD 6750M graphics with 512MB of video memory. The $1499 21.5-inch iMac has a 2.7GHz Core i5 quad core processor, a 1TB hard drive, and AMD Radeon HD 6770M graphics with 512MB of video memory. The $1699 27-inch iMac has the same processor, memory, and graphics as the $1499 iMac. At the top of the line sits a $1999 27-inch iMac with a 3.1GHz Core i5 quad core processor, a 1TB hard drive, and AMD Radeon HD 6970M graphics with 1GB of video memory.

All iMacs include an Apple Wireless Keyboard () and Magic Mouse (). If you buy an iMac through the Apple Online Store, you can swap the Magic Mouse for a Magic Trackpad () at no additional cost. If you think that the Magic Trackpad is a better input device, that’s good news.

Inside the iMacEach new standard-configuration iMac features a Core i5 quad-core processor. Based on Intel’s Sandy Bridge microarchitecture, the processors integrate the CPU, cache, and memory controller on one chip, allowing for fast data access over fewer buses. Each iMac has 6MB of shared L3 cache and support for Intel’s Turbo Boost 2.0, which allows the processor to automatically speed up cores when needed.

However, the Core i5 processors in the standard-configuration iMacs do not have Intel’s Hyper-Threading technology, which creates two virtual cores for each physical core present in the processor, improving performance. To get an iMac with a processor that has both Turbo Boost and Hyper-Threading, you’ll have to select the $200 Core i7 upgrade option for the $1499 21.5-inch iMac or $1999 27-inch iMac. (The standard-configuration Mac Pros and MacBook Pros have both Hyper-Threading and Turbo Boost.)

All iMacs come standard with 4GB of memory, installed as a pair of 2GB modules. When you order an iMac through the Apple Online Store, you have the option to upgrade the memory to 8GB (a pair of 4GB modules) on all iMac models for $200, or to 16GB (four 4GB modules) on the 27-inch models for $600. The iMac has four memory slots located at the bottom of the iMac that are user-accessible. Since two slots are empty when you buy an standard-configuration iMac, you can easily add more memory. The 21.5 inch iMac has support for up to 16GB of memory; third party companies are offering 32GB memory upgrades for the new 27-inch iMac.

The $1199 21.5-inch iMac has a 500GB, 7200-rpm hard drive and no upgrade options. The three other iMac models each have a 1TB 7200-rpm hard drive and options to upgrade to a 2TB hard drive for $150, a 256GB solid-state drive (SSD) for $500, or a combination of a 256GB SSD and either a 1TB 7200-rpm hard drive ($600) or a 2TB 7200-rpm hard drive ($750). Do-it-yourself storage upgrades are possible with the new iMac, but it requires a good amount of skill and intestinal fortitude on the user’s part—opening up the case involves using suction cups to remove the front pane of glass that is held in place by magnets. Such upgrades void your warranty, which may also be a deterrent from performing the surgery.

The new iMacs have support for Serial ATA-3 (SATA-3) drives capable of 6GBps speed, but the drives Apple installs and the BTO storage options conform to the SATA-2 specification and are capable of 3GBps speed. SATA-3 drives are becoming more common, however, and it's possible that Apple could offer SATA-3 drives in the future. Some companies, such as OWC, offer iMac upgrade services that can be used to install a SATA-3 drive. [Editor's note: OWC is reporting that the new iMacs use a proprietary cable that restricts the ability to upgrade the storage devices yourself.]

The new iMacs have a slot-loading, 8X SuperDrive that can burn dual-layer DVDs at 4X speeds, and a SDXD card slot for easy transfer of photo and video files from SD cards used in cameras and camcorders.

Thunderbolt

The 27-inch iMac has two Thunderbolt ports. They are indicated by the lightning-bolt icons and are located between the FireWire 800 and ethernet ports.A new external connection called Thunderbolt can be used to attach Mini DisplayPort monitors. Introduced earlier this year with the latest MacBook Pros, Thunderbolt can also be used with Thunderbolt-equipped storage devices. Thunderbolt offers data transfer speeds up of 10Gbit per second, which is 12 times faster than FireWire 800 and 20 times faster than USB 2.0. The 21.5-inch iMacs have one Thunderbolt port, while the 27-inch iMacs have two.

The catch is that at the time of the iMac’s release, Thunderbolt cables, drives, or adapters were not available, and it may be a while before Thunderbolt peripherals hit the market. When Thunderbolt was introduced with the MacBook Pro earlier this year, several companies said they had Thunderbolt products in the works, but many did not provide a solid timeline as to when products will be available to the public. So right now, Thunderbolt isn't the sole reason you should buy a new iMac, and fortunately, the iMac didn't lose any ports to make room for Thunderbolt. The iMac has four USB 2.0 ports and a FireWire 800 port to connect external hard drives, printers, and other devices.

The 2010 27-inch iMac allowed for external HDMI-based video sources (such as a Blu-ray player or game console) if you had an HDMI-to-Mini DisplayPort adapter—those adapters won’t work with the new iMacs, which require an HDMI-to-Thunderbolt adapter that isn’t available yet. If you have a Thunderbolt-equipped MacBook Pro, you can use the new iMac’s Target Display Mode feature, which allows you to use the iMac as a second display for the MacBook Pro. But again, the Thunderbolt cable that’s required to use the Target Display Mode feature wasn’t available during this review.